Pneumatic spring

ABSTRACT

A pneumatic spring comprising a tubular body, having a neck. A piston secured about the neck and movable within the body. Retaining means for securing the beaded ends of the body to supports and to the piston.

United States Patent Krejcir [151 3,682,464 [451 Aug. 8, 1972 PNEUMATICSPRING [72] Inventor: Oldrich Krejcir,

Czechoslovakia [73] Assignee: Autobrzdy, narodni podnik, Jablonec nadNisou, Czechoslovakia 22 Filed: July 29, 1970 211 Appl.No.: 59,141

Liberec,

[52] US. Cl ..267/65, 92/93 [51] Int. Cl. ..Fl6f 3/00 [58] Field ofSearch..92/93, 103; 267/65, 65 A, 65 B [56] References Cited UNITEDSTATES PATENTS 3,043,582 7/1962 Hirtreiter ..267/65B 3,081,075 3/1963Selman ..267/65A 2,922,637 1/1960 Bowser ..267/65 A 3,438,309 4/1969Boileau ..267/65 X 3,162,433 12/1964 Smirl ..267/65 A 2,999,681 9/ l 961Muller et a1. ..267/65 A 3,549,142 12/1970 Tilton ..92/103 X FOREIGNPATENTS OR APPLICATIONS 156,184 9/ 1921 Great Britain ..267/65 I PrimaryExaminerManin P. Schwadron Assistant Examiner-Leslie J. PayneAttorney-Richard Low and Murray Schafier [57] ABSTRACT A pneumaticspring comprising a tubular body, having a neck. A piston secured aboutthe neck and movable within the body. Retaining means for securing thebeaded ends of the body to supports and to the piston.

6 Claims, 3 Drawing Figures PATENT ED 8 I973 SHEET 1 0F 2 INVENTOROLQDRKH ALREJC, l R

WWO EY INVENTOR OLDRIcH KREACIR PATENTED 3 sum 2 0F 2 I. Ir

qt 1 E PNEUMATIC SPRING BACKGROUND OF THE INVENTION The presentinvention relates to pneumatic suspension systems for automobiles andsimilar vehicles.

Pneumatic or air springs are formed of a flexible bag, diaphragm body,or a container of rubber or rubberlike material, usually reinforced withfabric or metallic cords. Such devices are particularly suitable for useas suspension systems for automobiles, omnibusses, trucks, and similarvehicles.

Generally, beads are provided of rubber or rubberlike materialreinforced with hoops in a generally known manner, and fastened andsealed by the effect of air pressure inside the body of the pneumaticsprings by being forced against a seat provided on the upper part of apiston or a support plate. It is also common in diaphragm-type airsprings, particularly, to bend the lower edge of the bag or of thediaphragm over a rounded peak of a hollow piston and secure it by aplate tightly held by fasteners and vulcanized directly to thereinforced edges. In another known embodiment the beads are forced frombeneath the piston against an end of a conical or a pot-like pieceinserted into the piston of the pneumatic spring.

Although in all these cases the beads of the bag or the diaphragm havesimple shapes, their production is exacting and costly. They all requirethat the inside of the mould in which the body bags or diaphragrns arevulcanized in production be provided with a heating core, for mouldingthe beads, or at least other auxiliary parts. In addition, in all knownbag-type or diaphragmtype pneumatic springs, the bag or diaphragmbecomes deformed during spring action in the vicinity of the beads, andsince the wall of the bag or of the diaphragm at that point is always ofirregular thickness either because it extends continually or suddenlyinto the reinforced beads, or in some cases because of the accumulationand overflow of rubber from the beads during moulding and vulcanization,there is created by a sudden change of the shape and cross-section,harmful stresses which reduce the life of the device.

Another disadvantage occurs when the diameters of the two beads of thebag and of the diaphragm are substantially different. Here, the shape ofthe beads must be excessively changed during preparation of productionof the bag or of the diaphragm and they must be either extended ornarrowed. When this is done, the distribution of the cords, reinforcingthe bag or the diaphragm, is irregular and the harmful effects resultingfrom sudden changes of the shape and of the crosssection are increased.

It is also known that hollow pistons may be used for increasing thevolume of air in the pneumatic spring. However, if such hollow pistonsare produced by moulding, they are sometimes porous, and thendifficulties arise from leakage of air. This results in considerablelosses in the production by an excessive number of rejects, and thecosts are also increased by the necessity of a rigid and time consumingcontrol.

Numerous vehicles presently use pneumatic springs of the bellows-typefor springing. In such pneumatic springs it is common to connect andtighten the beads on both ends of the bellows with the fastening surfaceby means of safety or retaining rings having folds or laps or groovesfor locating the rings by means of screws. Though such bellows-typepneumatic springs have a sufficiently long life, they are alsoconsiderably stiff. As a rule, they do provide a comfortable ride. If itis desired to improve the quality of springing in such vehicles and tosubstitute bag-type pneumatic springs for bellows-type pneumaticsprings, it is necessary to change the system for fastening pneumaticsprings to a greater or lesser degree, and this is costly. At the sametime, it is also desirable that the fastening systems be identical, andat least some of the parts of both types of the interchanged pneumaticsprings should be in common to increase mass production and to reducethe costs.

When using any of the known types of pneumatic springs, it is necessaryto use a compression stop made as a rule from rubber, which limits thecompression of the pneumatic spring and prevents damage to the wheels.The stop is often located inside the pneumatic spring and it is thenmounted either on the upper fastening surface, or on the uppersupporting plate, or on the upper part of the pneumatic spring, andduring springing it rests on the front surface of the piston, or on theopposite partition of the supporting bracket, or the stop is reversed onthe piston, and it again rests on the opposite part. All this requiresadditional elements which raise the costs of production. It hastherefore already been proposed to provide a rubber rib on the lug or onthe wall of the bag, or of the diaphragm, at the place which, duringspringing, may come into contact with an opposite part. This rib wouldtake over the performance of an elastic stop. But this rib also producesand increases the effect of a sudden change of the shape andcross-section, reducing the life of the bag or of the diaphragm, andcomplicating the mould for the production.

It is the object of the present invention to provide a pneumatic springimproved over the prior art devices.

It is another object of the present invention to provide a pneumaticspring which is easily fabricated, and which may be inexpensivelyproduced.

It is another object of this present invention to provide a pneumaticspring which has improved and extended life, and which operates underimproved conditions, maintaining desired spring action and ratioswithout leakage or premature damage.

It is still another object to provide a pneumatic spring which isreadily interchangeable with existing and conventional springs andpneumatic systems.

The above objects, and others, together with numerous advantages, arefully described and illustrated in the following disclosure.

SUMMARY OF INVENTION According to the present invention, there isprovided a pneumatic spring comprising a flexible tubular body having anenlarged portion, an axially arranged smaller diameter neck, andradially outwardly directed beads, of the same diameter, at each end. Atubular piston surrounds the neck and has an outer diameter smaller thanthe enlarged body portion. Retaining means are provided at each end,having a groove for receiving and securing the respective beads; theretaining means are adapted to be fastened to respective supports, atleast one of which is movable. In this manner, the piston is movablewithin the body, under varying load conditions, while the beads aresecurely held and sealed.

Preferably, the tubular body is cylindrical, although it may be slightlyoval or conical. The piston is also preferably made of one piece in aunitary construction, with its adjacent retaining ring, although theymay be separately made and later glued or vulcanized together.

In accordance with the invention, the piston may be made of resilientmaterial which forms, in-situ, or by itself, a soft and resilient stopmember, limiting telescoping of piston into the body.

Other embodiments, features and preferred forms, as well as a fulldescription of the invention, follows.

DESCRIPTION OF DRAWINGS In the following description, reference is madeto the accompanying drawings in which:

FIG. 1 is an elevational sectional view of a pneumatic spring, embodyingthe principles of the present invention;

FIG. 2 is a view similar to FIG. 1, showing a modified piston andretaining ring; and

FIG. 3 is a similar view, enlarged, of the body of the spring alone.

In the drawings, like reference numerals are directed to like elements.

DESCRIPTION OF INVENTION Referring now more particularly to FIG. 1, thepneumatic spring shown is provided with a tubular flexible body 1 madeof rubber, synthetic, or similarly resilient material, such as plastic,reinforced in the conventional manner with fabric or metallic cords. Thebody 1 is provided at both of its open ends with beads 2 and 3respectively, each equal in diameter and turned or bent radiallyoutward. The upper bead 2 is inserted into the annular groove 4 of aconforming metallic safety or retaining ring 5, which itself is securedby suitable fasteners 6, such as screw or bolts, to a non-illustratedsupporting surface. In this manner, the beads 2 and 3 are secured andfirmly held between the retaining ring and the support.

The body, which is a bag symmetrical about a central longitudinal axis,has an axially central section 7 of generally circular or oval shape,which is preferably of diametric dimension, greater than the extent ofthe beads 2 and 3. Secured about a lower terminal neck portion 8 of thebody 1 is an annular piston member 9 which, for the purpose ofillustration, is shown as a hard material like cast metal or plastic andis of a substantially non-flexible nature when stressed by increasing ordecreasing pressure within the body 1. The piston 9 terminates at itsupper end in a rounded or beveled edge 10 and at its lower end in aradially outward annular safety or retaining ring 11 similar to theupper ring 5, in that it is provided with an axially outward facingannular groove 12 into which the lower bead 3 is secured. The piston 9is itself secured by suitable fasteners 12, of the screw or bolt type,to a supporting member which is not illustrated. The inner wall of theannular piston 9 is straight while the outer wall tapers inwardly fromthe round top 10 and curves in a manner to decrease the narrow diameterand then to increase until the circumference described at the base ofthe retaining ring 11 is greater than the circumference at the round top10.

The supporting members for both the upper and lower retaining rings andare preferably similar in nature to those employed in conventionalbellows type springs, and may comprise a supporting plate separable fromor integral with the chassis, superstructure or axle of the vehicle, abowl or surrounding housing member provided with an annular securingflange. In any event, the supporting member is provided with means forsealing the ends of the body to make it air tight, and at least, at oneend to provide means for introducing compressed air from a suitablesource into the interior of the body 1. Preferably, the lower bead orthe supporting for it are secured to the axle of the vehicle andconsequently able to move the piston 9 vertically within the body 1.However, it may under certain circumstances be desirable to mount theupper bead on its supporting member simultaneous to a movable member, inwhich case the body 1 and piston 9 can act in accordion fashion. Thedetails of supporting structure, covering, and protective housings,feeding of compressed air, etc., are all analogous to the conventionalbellows spring system to which those skilled in this art may makereference.

FIG. 2 illustrates a pneumatic spring similar to that shown in FIG. 1and like reference numerals are used for like elements. The differencebetween the device 1 1 shown in this figure, however, resides in thefact that the portion 9 forming the retaining ring comprises a separatepart 14, which is similar in form and function to the upper retainingring 5. The remaining portion of the 9' is a substantially cylindricalsleeve having a straight inner wall engaging the end portion of the bodyand a curved outer wall similar to that shown in FIG. 1. The top 10' ofthe piston 9 is rounded, while the lower portion is curved to mate withand meet the retaining ring 14, to which it is preferably vulcanized.The retaining ring 14 is provided with a groove 12' adapted to hold thehead 3, as well as screw fasteners 13, as previously described. As inthe case of the embodiment shown in FIG. 1, the retaining rings 5 and14, of FIG. 2 are preferably made of metal, such as steel or aluminum.The piston 9' however is preferably made of hardened rubber or syntheticwhich is resistant to elasticity caused by increased pressure within thebody 1, but does have certain resilient or soft qualities.

Illustrated in FIG. 1 in enlarged detail is a resilient body or bag 1,made of rubber, or synthetic material reinforced with fabric or metalliccords in the known manner, which is intended for use in the assembleddevices shown in FIGS. 1 and 2. The central free or radially extensibleportion 7 is made of a diameter and length determined by operationalfactors and spring rate requirements of the device. Thus, it can be ofany desired predetermined length and breadth. The body 1 is necked downat its lower end into a terminal portion 8, which is smaller in diameterthan the central or extensible portion 7. The axial length of the neck 8is defined by and conforms with the length of the piston. The beads 2and 3 are radially turned outward and then axially inward. They, ofcourse, may be reinforced also with metallic rings and loops, and are ofa size adapted to be secured with the conforming retaining rings.

Operatively, the pneumatic spring devices are placed in use, as seen inFIGS. 1 and 2, and assume the position shown under normal loading.Compressed air is fed to the interior of the body from the source, whichmay be a storage accumulator, compressor or similar device. In normalconditions, the piston 9 enters partially into the space of the body 1,delineated by the central or free portions 7 (or 7'), the telescopeenabling the piston to telescope or move axially in either direction. Ifthe load on the vehicle is increased, consequently increasing the loadon the pneumatic device, the piston 9 (or 9') is pressed axially intothe body. The wall of the portion 7 (7') becomes further bent, anddepending upon the load, envelopes the round top 10 and moves downwardlyagainst the curved outer wall of the piston 9 (9'). In this manner, thebody 1 is actually contracted, decreasing the interior area, andconsequently increasing the pressure of the air contained therein. Asthe pressure increases within the bag or body 1, the axially opposedsupport ing plate or means (not shown) are resiliently urged apart as inconvention compression springs. On occasion, the load may become sogreat that the piston 9 (9') would telescope completely within the body1 so that the rounded to 10 (10) would cause abutment against the upperretaining ring 5. In the case of the embodiment shown in FIG. 2, thisdoes not cause concern, since the rubber or synthetic material out ofwhich the piston is made will have suflicient resiliency and softness toavoid damaging the walls of the body 1. To

prevent such unwanted damage in the embodiment of FIG. 1, it may benecessary to provide a separate elastic stop or cushion for the hardenedpiston material.

When the load on the vehicle is reduced, as by the axle suddenlydropping or the vehicle being unloaded of weight, then the piston movesaxially outward, tending to straighten the body wall of the central freeportion 7 (7' The air pressure within the piston gradually reduces.

While the inner wall of the piston 9 (9) is shown as being straightaxially and cylindrical, and the terminal neck 8 of the body 1 alsocylindrical, each may be conformingly modified. For example, they may beshaped to have a slight conical taper, or may have one or moreshoulders, steps or grooves to facilitate assembly or operation.

The production of the bag of the pneumatic spring in accordance with theinvention is simple and non-exacting. The material of rubber and/orsynthetic, and cords for producing the body, can be prepared on acylindrical mandrel or core, and a simple mould is sufficient for thefinal shaping and vulcanization of the bag with the bead bent outwards,this mould requiring no heau'ng core and no internal pieces since thefinal shaping of the body can be accomplished in a similar manner as forbellows of the bellows-type pneumatic springs by means of a compressedinert gas fed into the mould. This insures a very homogeneous andcompact wall of uniform thickness. As long as the diameters of bothbeads are the same, or at least not substantially different, the shapeof the material for making the bag need not be excessively changedmanually after formation, which also insures a uniform distribution ofthe cords in the rubber wall of the bag. The uniform thickness of thewall, together with the uniform distribution of the cords, increase thelife of the body.

The fact that the wall of the body in the close vicinity of the beaddoes not become deformed for practical purposes during spring action ortelescoping, eliminates harmful efiects caused by sudden changes in theshape and cross-section under use, and also contributes to long life.

In comparison with known bag-type pneumatic springs, the pneumaticspring in accordance with the invention consists of a relatively lownumber of elements which are easy to produce. Due to the fact that onepart of the body is inserted into a hollow piston, the base of whichforms the safety ring, receiving the bead insures continued and securesealing. Even if the pistons are cast and are porous to a certainextent, increase of pressure or air volume within the bag will not causeair to leak because tightness is insured by the non-porous nature ofneck 8, which is inserted into the hollow piston. Moreover, the airvolume in the pneumatic spring, in accordance with the invention, may befurther altered, as required, for example, by a suitable shape of thecentral parts of the fastening surfaces; i.e., space fillers, enlargedmembers or bosses may be used to reduce the size of this interiorcavity.

The pneumatic spring, in accordance with the invention, can be easilydesigned so that at least the fundamental fastening dimensions of thebeads and of the retaining rings are the same as in analogousbellowstype pneumatic springs. Thus it becomes possible to achieveinterchangeability of both types of pneumatic springs and to save thecosts for the otherwise necessary reconstruction of the vehicles andsystems required to mount them. Improvement of the interchangeability ofthe two types of pneumatic springs increases the possibility of massproduction and a further reduction in the costs can be achieved if someof the elements of both types of interchanged pneumatic springs areidentical. For example, the retaining ring for connecting the upper headof the body may be the same, or may also be the lower retaining ring ofthe embodiment seen in FIG. 2. A hollow piston made in the manner of thepresent is convenient also from the point of view of production,particularly in case the outer curved diameter of the piston, since itis easier to form the moulds of the various parts in sand, or towithdraw the cast pieces from the moulds. If the cylindrical part of thepiston or at least its top consists of rubber, a separate rubber stopand its securing elements are not required, and this leads to a furtherincrease in the production economy of rubber springs, and hence also ofvehicles.

Although the above described examples of pneumatic springs in accordancewith the invention have been discussed in connection with vehiclespringing, it is obvious that the advantages of the solution inaccordance with this invention may be used whenever pneumatic springsare usually employed, for example, for springing the bases of machines,and in other similar cases. Various modifications may be made to theshape, size, and form of the body as well as the piston. It is thereforeintended that the preceding description is illustrative only, and shouldnot be taken as limiting the present invention in any manner.

What is claimed is:

1. A pneumatic spring comprising a flexible tubular body having anenlarged portion, an axially arranged tubular neck portion of smallerdiameter and radially outwardly directed beads at each end having alarger diameter than said tubular neck portion, an elongated tubularpiston surrounding the neck and having an outer diameter smaller thanthe enlarged portion, said piston comprising a hollow tubular sleevehaving a cylindrical inner surface and a curved outer surface,

said outer surface having a rounded top edge and tapering inwardly alongits length to a predetermined point and then outwardly to a bottom edge,the bottom edge having a diameter greater than the diameter of the topedge and having a groove for receiving one of the beads of said body,retaining means at each end of said body for securing the respectivebeads, said retaining means being adapted to be fastened to respectivesupports, at least one of which is axially movable, to thereby causesaid piston to be telescopingly movable within the body, said bodyrolling along the outer surface of said piston under varying loadconditions applied to said supports.

2. The spring according to claim 1 wherein said body comprises an openended bag symmetrical about a cen-

1. A pneumatic spring comprising a flexible tubular body having anenlarged portion, an axially arranged tubular neck portion of smallerdiameter and radially outwardly directed beads at each end having alarger diameter than said tubular neck portion, an elongated tubularpiston surrounding the neck and having an outer diameter smaller thanthe enlarged portion, said piston comprising a hollow tubular sleevehaving a cylindrical inner surface and a curved outer surface, saidouter surface having a rounded top edge and tapering inwardly along itslength to a predetermined point and then outwardly to a bottom edge, thebottom edge having a diameter greater than the diameter of the top edgeand having a groove for receiving one of the beads of said body,retaining means at each end of said body for securing the respectivebeads, said retaining means being adapted to be fastened to respectivesupports, at least one of which is axially movable, to thereby causesaid piston to be telescopingly movable within the body, said bodyrolling along the outer surface of said piston under varying loadconditions applied to said supports.
 2. The spring according to claim 1wherein said body comprises an open ended bag symmetrical about acentral longitudinal axis.
 3. The spring according to claim 2, whereinsaid body is substantially cylindrical.
 4. The spring according to claim1 wherein said piston and the adjacent retaining ring are unitarilyformed as one piece.
 5. The spring according to claim 1 wherein saidpiston and the adjacent retaining ring are separately formed.
 6. Thespring according to claim 1, wherein said piston is formed of resilientmaterial and provides at its upper edge a stop adapted to abut, underexcessive loads, with the interior of the body.